1. Field of the Invention
The present invention relates to a cylinder lock with a removable core of the kind comprising:
a cylinder lock casing having interior wall surfaces defining an axially extending cavity with an insertion opening,
a removable cylinder lock core which is axially insertable into said cavity through said insertion opening, said lock core having an upper, substantially massive part with a row of holes for accommodating locking tumblers, and a lower part defining a cylindrical bore extending axially therethrough,
a cylindrical, rotatable key plug located in said cylindrical bore and having a longitudinal key slot for receiving a key co-operating with said locking tumblers, and
a retainer member being transversely movable in a chamber in the upper part of said lock core between a first position, in which it positively locks said lock core in its axially inserted position, and a second position, in which said lock core may be axially inserted into or retracted from said casing, said retainer member having a locking surface facing towards said insertion opening and engaging with said casing when said retainer member is in said first position.
2. Description of the Background Art
Such a lock with a removable core is previously known, e.g., from U.S. Pat. No. 4,328,690 (Medeco) and WO 96/36782 (Winloc). In the prior art locks, the locking surface on the retainer member is formed on an outwardly projecting locking lug, which engages with a recessed portion of the casing so as to retain the lock core in its inserted position. The locking lug can be moved to a second, releasing position where it is instead accommodated in a recess in the massive upper part of the lock core. Then, the whole lock core with the key plug may be retracted axially from the lock casing by a sliding movement. The lock core has an outer contour corresponding to the cross-sectional shape of the cavity of the casing, normally in the general shape of an xe2x80x9c8xe2x80x9d, with a slight play therebetween to permit the relative sliding movement.
With such a system, it is of course possible to replace a lock core of a first kind by another lock core of a second kind, so long as the cross-sectional dimensions of the lock cores are the same and the locking lugs correspond to each other. However, for economic and security reasons, it is in the interest of any lock manufacturer and any authorized user of the system that the lock cores cannot be replaced by other kinds of lock cores, e.g., made by another manufacturer.
Furthermore, a locking lug projecting into a recess in the wall of the casing may be destroyed by a machining operation, e.g., by drilling axially into the casing wall from the front side of the lock in the region where the recess and the engaging locking lug are located, normally in the vicinity of the mid-portion of the lock core in case it is formed like an xe2x80x9c8xe2x80x9d.
Against this background, the main object of the present invention is to provide a novel embodiment of the locking means holding the lock core in its inserted position in the casing so as to increase the security of the lock.
Other objects are to provide high security against unauthorized retraction or replacement of the lock core and to enable rational but controlled manufacture of the lock casings and the associated lock cores and key plugs.
The stated main object is achieved in that the lock casing comprises a locking projection, which protrudes from one of the interior wall surfaces so as to project inwardly from said inner cross sectional contour and to engage with the locking surface of the retainer member, when the latter is in the first position, said lock core and said retainer member being adapted to form a longitudinal recess located adjacent to said chamber in the region of said outer cross sectional contour and being dimensioned to accommodate said locking projection when said retainer member is located in said second position and said lock core is being inserted into or retracted from said casing.
It is not a trivial matter to arrange such inwardly projecting locking projections, since a locking projection which protrudes inwards from the cavity wall will normally interfere with the contour of the lock core, which matches the inner contour of the casing. However, it is then possible to let the projection fit freely into the above-mentioned longitudinal recess of the lock core.
Preferably, the longitudinal recess of the lock core is a rectilinear slot, e.g., extending from one end thereof, and the retainer member is preferably dimensioned to leave said rectilinear slot at least partially free when being situated in said second position, so as to permit axial displacement of said locking projection along said rectilinear slot during insertion or retraction of the lock core, and to effectively block access to said rectilinear slot when being situated in said first position, so as to positively lock said retainer member and said lock core in their axially inserted positions in said cavity of said casing.
The present invention also concerns a removable lock core as such and including a retainer member, the lock core and the retainer member being adapted to form a longitudinal recess dimensioned to accommodate, when said retainer member is located in said second position, a locking projection protruding from an interior wall of an associated casing radially inwards from said inner cross sectional contour of the casing.
The retainer member may have a limited circumferential extension, which is substantially supplemental to an axially continuous wall portion defining a part of the cylindrical bore, or it may be circumferentially closed so as to form a circular-cylindrical sleeve element, in which case there is an axially extending slot portion in said sleeve element being aligned to the rectilinear slot when the retainer member is located in said second position, an axially limited recess being dimensioned to accommodate the locking projection.
The locking surface on the retainer member may be formed on an end surface of a longitudinal edge portion thereof, or on a transversely projecting, axially limited tongue, or on a wall portion defining an axially limited recess.
In any case, the removable core can only be replaced by a core of the same kind, i.e. being designed to accommodate the inwardly projecting locking projection while being inserted into the casing. Furthermore, the locking projection is protected by the core itself when the latter is located in its fully inserted position.
The locking projection should be long enough to engage with the locking surface on the retainer member. However, the radial extension is preferably limited so as not to interfere directly with the rotatable key plug. Most preferably, the radial extension of the locking projection is such as to reach into close vicinity of the wall surface of said cylindrical bore.
In a further developed embodiment according to the invention, the casing has, in addition to the locking projection, an axially limited recessed portion in one of said interior wall surfaces, and the locking means of the retainer member comprises, in addition to an axially limited recess, a locking lug fitting into said recessed portion of the casing when the retainer member is located in said first position. Such a locking lug may be located in close vicinity to said axially limited recess.
These and other advantageous features are stated in the dependant claims and will be apparent from the detailed description below.